Ink-jet printers, owing to the development of models of higher performance, have been finding utility for a wide variety of applications, including personal applications, office applications, business applications, recording applications, color display applications and color photo applications. Concerning pigment inks, on the other hand, there is a move toward use of still smaller pigment particles in inks with a view to achieving improvements in pigment vividness, brightness, color density and the like. There is also a move toward smaller jetted droplets (ink droplets) in order to keep in step with the move toward higher printing speed and higher image quality by improvements in printers. These improvements have brought about high image quality for coated paper for ink-jet recording, especially for photographic paper and wide format paper but, when printed on non-coated paper called “plain paper”, ink droplets penetrate into paper fibers, resulting in the development of a problem that the printing color density, in other words, the color developing property is lowered.
An object of the present invention is to provide a water-based pigment ink for use in ink-jet recording, which can form an image good in chroma and density and excellent in print quality even when printing is performed on plain paper.